.TH __env_lock 3 "" "" ""
.SH SYNOPSIS
__env_lock, __env_unlock \- lock environ variable
.SH ANSI_SYNOPSIS
#include "envlock.h"
.br
void __env_lock (struct _reent *
.IR reent );
.br
void __env_unlock (struct _reent *
.IR reent );
.br
.SH TRAD_SYNOPSIS
void __env_lock(
.IR reent )
.br
struct _reent *
.IR reent ;
.br

void __env_unlock(
.IR reent )
.br
struct _reent *
.IR reent ;
.br
.SH DESCRIPTION
The 
.BR setenv 
family of routines call these functions when they need
to modify the environ variable. The version of these routines supplied
in the library does not do anything. If multiple threads of execution
can call 
.BR setenv ,
or if 
.BR setenv 
can be called reentrantly, then
you need to define your own versions of these functions in order to
safely lock the memory pool during a call. If you do not, the memory
pool may become corrupted.

A call to 
.BR setenv 
may call 
.BR __env_lock 
recursively; that is,
the sequence of calls may go 
.BR __env_lock ,
.BR __env_lock ,
.BR __env_unlock ,
.BR __env_unlock .
Any implementation of these
routines must be careful to avoid causing a thread to wait for a lock
that it already holds.
.SH SOURCE
src/newlib/libc/stdlib/envlock.c
